1. Field of the Invention
The present invention relates to a method for manufacturing a pattern multilayer body in which a plurality of pattern layers are laminated, and a mask set for forming a pattern in each pattern layer in the pattern multilayer body.
2. Description of the Related Art
Recently, in conjunction with the high recording density of hard disk drives (HDD), there is a demand for improvement in the performance of thin film magnetic heads. As the thin film magnetic head, composite type thin film magnetic heads having a configuration in which a reproducing head having a read-only magnetoresistive effect element (MR element) and a recording head having a write-only induction-type magnetic transduction element are laminated are widely used. In particular, in conjunction with higher recording densitys of hard disk drives, a thin film magnetic head having a reproducing head where a plurality of MR elements with the same configuration are arranged along a lamination direction has been proposed. Conventionally, a reproducing head for a magnetic tape in which a plurality of MR elements are arranged along a lamination direction is known (JP Patent Application No. 2002-157710).
In such a pattern multilayer body where a plurality of pattern layers, such as thin film magnetic heads, are laminated, a position gap in a direction that is orthogonal to the lamination direction between the element patterns of each pattern layer respectively affects its quality. Consequently, when the pattern multilayer body above is manufactured, an overlay pattern and the element pattern are formed at the same time, and the position gap between the element patterns of each pattern layer is measured by measuring a position gap in a direction orthogonal to the lamination direction using the overlay pattern.
Conventionally, the pattern multilayer body having the element pattern in each pattern layer is manufactured as discussed below. Furthermore, a method for manufacturing a thin film magnetic head having a reproducing head where a plurality of MR elements are arranged in the lamination direction is explained below as an example. FIGS. 19A to 19C are cross-sectional views schematically showing each step of a conventional method for manufacturing a reproducing head. Furthermore, in FIGS. 19A to 19C, fabrication steps of a reproducing head are shown on the left side, and fabrication steps of an overlay pattern are shown on the right side.
First, an insulation layer 1030, such as Al2O3 or SiO2, and a first lower part shield layer 140 are formed within an MR element formation region on a substrate 1100, and the insulation layer 1030 is laminated onto an overlay pattern formation region. Then, a first MR element layer 1210, such as metal, and a positive-type photoresist film 400 are lamination-formed on the first lower part shield layer 140 and the insulation layer 1030 in respective order and the positive-type photoresist film 400 is exposed using a first mask 301 (see FIG. 19A).
The first mask 301 has a light shielding part 3011 corresponding to a resist pattern for forming a magnetoresistive effect part (MR part) 120 of the first MR element and a light shielding part 3012 corresponding to a resist pattern for forming a first overlay pattern 1211.
After the exposure via the first mask 301, a resist pattern is formed on the first MR element layer 1210 by development using a predetermined developing solution and the like, and the MR part 120 of the first MR element and the first overlay pattern 1211 are formed by applying a milling treatment using the resist pattern as a mask (see FIG. 19B). Furthermore, a nearly-rectangular frame-state pattern is shown as the first overlay pattern 1211.
Next, side shield layers 150 are formed on both sides of the MR part 120, and a first upper part shield layer 130, an intermediate layer 1050 and a second lower part shield layer 240 are formed on them in respective order, and an insulation layer 1070, such as Al2O3 or SiO2, to coat the first overlay pattern 1211 is formed at the same time. Then, a second MR element layer 2210, such as metal, is formed on the second lower part shield layer 240, and a positive-type photoresist film 500 is formed on the upper layer of the second MR element layer 2210 and the insulation layer 1050. Furthermore, since light does not penetrate the metal and the like forming the second MR element layer 2210, the second MR element layer 2210 is not formed on the insulation layer 1050. Then, the positive-type photoresist film 500 is exposed using a second mask 302 (see FIG. 19C).
The second mask 302 has a light shielding part 3021 corresponding to a resist pattern for forming a magnetoresistive effect part (MR part) 220 of the second MR element, and a light shielding part 3022 corresponding to a resist pattern as a second overlay pattern.
Then, after the exposure via the second mask 302, development using a predetermined developing solution and the like is conducted, a resist pattern is formed on the second element layer 2210, and a second overlay pattern (a resist pattern) is formed on the insulation layer 1070. Furthermore, as the second overlay pattern, a nearly-rectangular pattern positioned within the first overlay pattern 1211, which is in a nearly-rectangular state in a planar view, is shown. The first overlay pattern 1211 and the second overlay pattern are overlay patterns referred to as a so-called box-in-box type, respectively.
A position gap between the two overlay patterns can be measured by detecting the first overlay pattern 1211 and the second overlay pattern formed as mentioned above from the upper side in the lamination direction. The position gap distance between the overlay patterns is evaluated as the position gap distance between the MR part 120 of the first MR element and the MR part 220 of the second MR element.
In the manufacturing method above, in order to form the first overlay pattern 1211 and the second overlay pattern, two different masks (the first mask 301 and the second mask 302) are used. In each of the masks 301 and 302, a manufacturing error regarding the positions of the light shielding parts 3012 and 3022 may be caused. Consequently, the position gap measurement accuracy between the first overlay pattern 1211 and the second overlay pattern is affected not only by alignment accuracy upon exposure using these two different masks (the first mask 301 and the second mask 302), respectively, but also by a manufacturing error between the two masks 301 and 302. In other words, even if the alignment upon the exposure of the two masks 301 and 302 above is performed with high accuracy, the position gap measurement accuracy between the first overlay pattern 1211 and the second overlay pattern is decreased due to the manufacturing error above. In association with this, the position gap measurement accuracy between the MR parts 120 and 220 of the first and second MR elements is decreased.
In response to the high recording densitys of hard disk drives, at present, positional accuracy between element patterns of each pattern layer in the pattern multilayer body, such as a thin film magnetic head, is now more strictly in demand than before. In the meantime, a decrease in position gap measurement accuracy based upon a manufacturing error between/among a plurality of masks that are used for forming the overlay patterns has been becoming a problem.
Also, in a manufacturing process of a nonvolatile semiconductor memory element and the like having a floating gate, even in the pattern multilayer body that is manufactured by conducting patterning steps a plurality of times using a plurality of masks having the same light shielding pattern, the reduction in the position gap measurement accuracy based upon a manufacturing error between/among a plurality of masks is a problem.